How many people had London Irish down as Guinness Premiership finalists when the season started? The Exiles still have to complete the heist but this display will have caused some unease in the East Midlands. Irish also have Mike Catt, the Macavity of English back play and a man still writing his own implausible screenplays. Catt v Tigers has all the makings of a gripping tooth-and-claw showdown and it will be no foregone conclusion.

The presence at Twickenham on Saturday of the 37-year-old former England back will certainly soften neutral hearts. When he played his last game for Bath in the 2004 final against Wasps, he did so as an emergency full-back having originally been left out of the ­starting line-up by the Australian coaching combo of John Connolly and Michael Foley. "To this day I believe that had I been picked at 10 we would have won that game," wrote Catt in his autobiography. Now, against all odds, he has a chance to make amends.

Whether it proves the player-coach's last game of competitive rugby, ­however, depends partly on circumstances outside his control. Irish's head coach, Toby Booth, has signed two fly-halves for next season, both of whom are currently injured. The situation may yet prolong the career of rugby's old father time by a few more months. "My future as a player is the final against Leicester this weekend," said Catt. "Then I'll sit down with the family, Boothy and everyone at Irish and make the right decision. If I had the opportunity to take a back seat I probably would. At the moment, however, I might have to do another pre-season."

As he was also quick to stress, this weekend will not solely be about him. How could it be when the likes of the brothers Armitage, Paul Hodgson, Bob Casey and Declan Danaher are giving so much to the Exiles' cause?

Despite struggling to get any sort of foothold early on against Harlequins, Irish held their own physically and pulled away impressively after a scoreless first-half in which Quins missed four penalty attempts. Tries from the Newcastle-bound James Hudson and Catt himself, the latter pouncing on a floated pass from a former England ­colleague, Andy Gomarsall, sealed the deal and the margin would have been greater but for brave cover-tackling from the home full-back, Mike Brown.

The one blot on the landscape was the knee ligament injury suffered by the Exiles lock Nick Kennedy which looks set to put him out of the final as well as England's summer Tests against Argentina. Even without Kennedy, though, Catt reckons Irish have a chance at Twickenham.

"We're a lot smarter than we were," he said. "We were in a Heineken Cup semi-final last year and we learned a hell of a lot. In the last 15-20 minutes teams start struggling against us. Playing in a Premiership final is a brand new experience for our youngsters but it's something we're going to savour. We've got ourselves a ­lottery ticket and it's 50-50 who wins it. It's going to be a massive ask to beat Leicester but we'll give it a go."

Even Quins' director of rugby, Dean Richards, who won trophies by the bucketload during his time at Welford Road, is not entirely convinced Leicester will ­prevail against an Irish team who transparently enjoy each other's company.

"I don't think their front row competes with the Leicester front row but their back row and back line are extremely good," he said. "If you look at the pace and power they've got in the back line it's a match for anyone in the Premiership. If they get even 40% of the ball I think they could be quite dangerous." As Irish's two regular-season league games against Leicester ended in defeats by two and three points, a final-day walkover seems unlikely.

One or two Exiles may also have forced their way into Ian McGeechan's ­thinking as the Lions head coach ponders how to fill vacancies at scrum-half and in midfield. If he has a more feisty No9 at his disposal than Hodgson he is a lucky man and Delon Armitage could yet become the athletic, hard-edged No13 that all good sides crave. In the end, with Catt as puppet-master, Irish are always willing to give it a go. "Catty spent two days in bed with flu this week but we still started him because we know how important he is to controlling our attack," said Booth. "He's got a fantastic appetite to be doing what he's doing at 37 years of age. People just dream about that situation."